A Lamborghini Aventador, produced by Lamborghini SpA, is seen on display during the first press day of the Geneva International Motor Show in Geneva, Switzerland, on Tuesday, March 6, 2012. The 82nd Geneva International Motor Show will showcase the latest models from the auto industry's leading manufacturers at the Palexpo exhibition centre this week. Photographer: Chris Ratcliffe/Bloomberg

EMPLOYMENT

U.S. workers' efficiency tapering off

The productivity of U.S. workers rose at a slower pace in the fourth quarter and labor costs jumped, indicating businesses are reaching the limit of wringing efficiency from their workforce.

The measure of employee output per hour climbed at a 0.9 percent annual rate, after a 1.8 percent gain in the prior three months, revised figures from the Labor Department showed. Expenses per worker climbed at a 2.8 percent rate, more than twice as much as previously estimated.

Productivity will probably remain restrained as businesses gain confidence in the economic expansion and take on more workers to meet growing demand. Nonetheless, rising labor costs and slowing efficiency may put pressure on corporate profits.

Lamborghini sales keep pace with 2011

Lamborghini had a "good start" to the year after selling the $2.76 million Aventador J shown this week in Geneva, CEO Stephan Winkelmann said.

"We delivered in the first two months almost the same amount of cars we sold in the first quarter of 2011, so this is a good success," Winkelmann said.

Winkelmann said he remains cautious for 2012 as a deceleration of the Chinese market and the debt crisis in Europe make it difficult for the Italian company to give forecasts.

Lamborghini boosted deliveries 23 percent last year to 1,602 super cars. The Volkswagen AG unit hasn't had any orders canceled thus far because of the European crisis, he said.

FOOD

Crunch time for Taco Bell's Doritos shell

At midnight Wednesday, Taco Bell rolled out Doritos Locos Tacos at its nearly 5,600 restaurants nationwide. The fast-food chain called the tacos, which use shells made out of Nacho Cheese Doritos, the biggest product launch in its 50-year history. It plans to introduce a Doritos Cool Ranch taco shell this fall.

Taco Bell, a unit of Yum Brands Inc., said it expects to spend up to $75 million to advertise the tacos - about three times more than typical promotions of new menu rollouts.

The tacos come as Taco Bell attempts to rebound from the bad publicity generated by a lawsuit a year ago that alleged the meat filling served at its restaurants didn't have enough beef to be called that. The suit was dropped three months later.

ENERGY

Warm winter leaves surplus of natural gas

The price of natural gas dropped to the lowest level in a decade Wednesday as a mild winter comes to a close with a huge surplus of the fuel on hand.

Natural gas supplies typically drop in the winter as homes and business crank up the heat. But relatively warm temperatures, combined with a boom in production, has left storage facilities bloated with more gas than normal.

Natural gas futures fell by 4.5 cents to $2.311 per 1,000 cubic feet in New York. That's the lowest price since Feb. 25, 2002, and down 70 cents from the start of the year.

Supplies have been growing in recent years as drillers have learned to use a controversial drilling technology called fracking to tap vast reserves of natural gas trapped in shale formations under several states.

The government said last week that supplies were 45 percent larger than average for this time of year.